Patent GB-573392-A (GB)
Title: Improvements in and relating to grinding or abrading machines
IPC: B24B3/04
Filed: 1944-02-28
Abstract: 573,392. Grinding &c. machines. ASSOCIATED EQUIPMENT CO., Ltd., and FRANCIS, A. A. J. Feb. 28, 1944, No. 3667. [Class 60] In a machine for grinding helical or straight flutes &c. in shafts &c., for example, splined shafts, gear cutters and hobs, the work to be ground is traversed relatively to the grinding- tool, by a lead screw, and is rotated through worm gearing, the cut being applied by periodic small additional rotation of the work effected by axial translation of the worm. The machine comprises an indexing-head b, Fig. 1, mounted on a work-table d reciprocable on a slide s angularly adjustable, to suit the helix angle of the work, on a cross-slide e mounted on a knee g adjustable on ways r on a column m, the work h being carried by an arbor i between centres j, k and operated upon by one or other of two grinding-wheels p, q carried by a wheel head o mounted on the column m. The work is driven by a motor, not shown, mounted on the column m, through a telescopic shaft v and gearing including bevel gearing y, 1 and reversing gearing 8, 9, 12, driving a splined shaft 2 mounted in the slide s, which, through'gears 3, 4, drives a lead screw 5 mounted in the carriage d ; to allow for backlash in the gearing, the lead screw nut is slidable endwise on the slide s. The wheel head o, Fig. 8, has therein two horizontal spindles carrying, respectively, a disc or cup wheel p, and a small cone wheel q, the upper spindle being driven direct by a motor 14 and the lower spindle through belt gearing 17-19. When grinding helices, the work arbor i is rotated alternately by two mechanisms, one during grinding and the other during indexing ; the indexing drive is through a friction clutch which slips during the grinding drive, acting as a brake on the rotating parts. The drives are taken from the motor, the first mechanism comprising a gear 20 on the lead screw, Fig. 11, a tumbler gear 21, change speed gearing, a pair of skew gears 23, and a worm 24 and worm-wheel 25, this wheel being mounted on a rotatable housing 26 carrying an index plunger 27 co-operating with an index plate 28 secured to the work spindle 29 ; the spindle is supported in bearings 30, 32 and is loaded by a spring 31 which also loads the friction clutch 57, 58. In order to apply feed or cut to the work, the worm 24 is adapted to act also as a rack, thus imparting to the work spindle intermittent small partial additional rotation ; for this purpose, the worm shaft is splined to slide in one of the skew gears 35, Fig. 12, and the worm shaft thrust housing 37 has a screwed extension 36 engaged by a nut 38 carrying a ratchet-wheel 39. The wheel 39 is actuated by a pawl, moved by a spring-loaded plunger 42 normally held up by a load-and-fire trigger 43, which is released once per revolution of the work by a cam 44 having one-way rotation only, release of the trigger 43 by the cam allowing the plunger 42 to drop, thus actuating the pawl. The amount of movement given by the pawl is adjustable by a knob 46 which regulates the movement of the plunger, which is lifted; to set the mechanism, by a trip lever 47 on the table d associated with an adjustable dog 48 on a stationary slide 49. The feed continues until axial movement of the worm 24 is arrested by a stop 50 set by a knob 51 and scale to give the required size to the work. During the indexing of the work, the drive is through skew gears 54, worm 55, worm-wheel 56 and the friction clutch.